1. Field
The present embodiments relate to an input device.
2. Related Art
In recent years, various input devices (interfaces) interposed between an electronic device, for example, a PC (personal computer) and a mobile phone, and a person who performs an input operation to the electronic device (hereinafter referred to as an “operator”) have been proposed. Such input devices include, for example, a PC keyboard, a mouse, a touch pad type input device, and a numeric keypad used in a mobile phone. With the touch pad type input device, the absolute position input used in the handwriting input or the like and the relative position input used in the movement of a mouse pointer or the like can be easily performed in a limited area of an input screen. Thus, the touch pad type input device is frequently used in a mobile electronic device, such as a notebook PC, a PDA (Personal Digital Assistant), or a tablet PC.
A conventional touch pad type input device includes, for example, an X-detecting electrode having a plurality of linear electrodes extending in a horizontal direction. A common electrode has a plurality of linear electrodes, which are aligned between the respective linear electrodes of the X-detecting electrode on the surface formed with the X-detecting electrode and which extend parallel to the linear electrodes of the X-detecting electrode. A Y-detecting electrode has a plurality of linear electrodes extending in a vertical direction. Since a pulse voltage is applied to the linear electrodes of the common electrode, the linear electrodes of the X-detecting electrode and the Y-detecting electrode are both electrostatically coupled to the linear electrodes of the common electrode.
The surface formed with the X-detecting electrode and the common electrode and the surface formed with the Y-detecting electrode are superimposed on each other, with the two surfaces parallel to and not in contact with each other. Either one of the surface formed with the X-detecting electrode and the common electrode or the surface formed with the Y-detecting electrode is provided with a protection sheet, which forms an input screen for an operation tool, such as a finger and an input pen.
With the conventional touch pad type input device, when the protection sheet forming the input screen is traced with the operation tool, such as the finger or an input pen, the linear electrodes of the X-detecting electrode and the Y-detecting electrode corresponding to the traced region of the protection sheet change in charge capacity, and thus the absolute position (i.e., the absolute coordinate) of the operation tool can be detected.
In the conventional touch pad type input device, upon receipt of an input signal sent by an input mode switch separately provided to the conventional touch pad type input device or a host electronic device, a control unit of the electronic device (i.e., the host electronic device) provided with the touch pad type input device controls the switching of the input mode between the absolute position input used in the handwriting input or the like and the relative position input used in the movement of the mouse pointer or the like (see Japanese Patent No. 3276079 and Japanese Unexamined Patent Application Publication No. 7-44306).
For example, as illustrated in FIG. 9B, it is now assumed that a letter A has been input through the handwriting input in a detection section (i.e., a touch pad section) 102a of a touch pad type input device 101 by using an operation tool H, such as a finger of an operator. The letter A input through the handwriting input is displayed on a display screen (i.e., an operation screen) 105 as illustrated in FIG. 9A. As illustrated in FIG. 10A, to search an English word starting with the letter A displayed on the display screen 105, there arises a need to change the input mode of the detection section (i.e., the touch pad section) 102a from a handwriting input mode for inputting the absolute position to a search mode for selecting a desired English word by moving a mouse pointer M.
This changing (switching) of the input mode is carried out by operating, for example, a mechanical input mode switch 103 formed separately from a touch pad 102 as illustrated in FIG. 9B or an input mode switch button 104 displayed on the display screen 105 as illustrated in FIG. 9A. Upon operation of the mechanical input mode switch 103 or the input mode switch button 104, the touch pad type input device 101 sends an output signal for switching the input mode to a control unit (not illustrated) of a host electronic device.
The control unit (not illustrated) of the host electronic device performs processing in accordance with the signal input therein, and sends a mode switch command to the touch pad type input device 101. The touch pad type input device 101 then analyses the mode switch command and sends an according output signal to the control unit of the host electronic device. Thereby, the absolute position input mode is switched to the relative position input mode, or the displayed content of the display screen 105 illustrated in FIG. 9A is switched to the displayed content of the display screen 105 illustrated in FIG. 10A.
Accordingly, as illustrated in FIGS. 10A and 10B, the detection section (i.e., the touch pad section) 102a, in which the input mode has been changed from the absolute position input for the handwriting input or the like, can detect the relative position input for moving the mouse pointer M.
As the electronic device (i.e., the host electronic device) provided with the touch pad type input device 101 has been reduced in size, it may become physically difficult to separately provide the mechanical input mode switch 103 around the touch pad 102 due to the size limit of a housing of the host electronic device.
As the content displayed on the display screen 105 has become diverse and complex, a space for displaying the input mode switch button 104 displayed on the display screen 105 may not be secured.
During the operation of the above-described mechanical input mode switch 103 or input mode switch button 104, the input operation accompanying a long-distance movement needs to be consciously carried out from a touch pad input screen 102e to the mechanical input mode switch 103 or from the last input point on the display screen 105 to the input mode switch button 104. This hinders prompt switching of the input mode.
The above-described switching of the input mode is controlled by the control unit of the host electronic device provided with the input device, such as the touch pad type input device 101. Therefore, the control unit of the host electronic device, which is subject to burdens, is forced to be further burdened.
In addition, since the touch pad type input device 101 performs the input operation by detecting the change in the electrostatic capacitance, the common electrode needs to be constantly applied with the pulse voltage. Thus, unnecessary power consumption is increased during a time in which the touch pad type input device 101 is not in operation.